Overclocking Llano can be quite a daunting task. The only way to overclock Llano is via the reference clock, which is 100MHz per default (PCIe interface clock speed). When raising the reference clock, the clock of all interfaces like SATA will be raised as well, potentially leading to instability.
At certain clocks dividers kick in to bring the interface clock speeds back to normal levels. For example a setting of 120MHz might be unstable, but a setting of 133MHz might again work without a hassle. With a reference clock of 133MHz the CPU is already operating at 3857MHz and the GPU at 798MHz. Depending on cooling and the quality of the chip, this may or may not run stable.
In our own testing we weren't able to overclock the chip at all. This could be due to various reasons, which we weren't able to pinpoint because of time constraints. Our colleages at Overclockers.com list a few reasons
why overclocking Llano might fail. However, we were able to reach a stable undervolt of -0.275V, which clearly shows that there is a lot of potential in either direction, so we assume something else was holding us back.
At this point we'd like to state, that we don't think the A-series APUs based on Llano are a particularly good choice for overclockers. Despite the theoretically superior 32nm manufacturing, the 45nm chips of the Athlon II and Phenom II lines overclock a bit better better on similar cooling solutions. If you are gunning for performance, you are most certainly not interested in the integrated GPU either. So if you want to overclock for greater performance, we'd suggest to get a Phenom II and a discrete GPU corresponding to your needs instead. For Llano we'd rather try to minimize power consumption by undervolting. As always, your mileage may vary.
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